Does the MONARC transobturator suburethral sling cause post-operative voiding dysfunction? A prospective study

The aim of this study was to compare pre-operative and post-operative voiding parameters following insertion of the MONARC transobturator tape (TOT), for treating women with urodynamic stress incontinence. This prospective observational study was conducted at a tertiary referral urogynaecology unit, in North Queensland, involving 83 women who were prospectively assessed pre-operatively and at 6–8 weeks following the procedure. Information collected included patient demographics, concomitant surgery, pre-operative and post-operative symptomatology (using validated questionnaires), and pre-operative and post-operative urodynamic parameters. Parameters used to assess voiding function included symptoms of voiding difficulty (incomplete emptying and irritative symptoms) as well as objective parameters including maximum flow rate (Q_max), adjusted maximum flow rate (Q_maxadj) using the Liverpool nomogram (LN), maximal urethral pressure, and post-void residual (PVR). Pre-operative average Q_max was 23.7 ml/s compared to 21.1 ml/s post-operatively (p=0.064). When the Q_max was adjusted for voided volume using the LN, Q_maxadj was seen to decrease significantly from 26 ml/s to 18 ml/s (p<0.05). Women with PVR>50 ml did not differ significantly pre-operatively and post-operatively, 5/83(6%) vs 7/83 (8.4%) (p=0.75). The number of women with a flow rate <10th centile on LN was 22 (26.5%) pre-operatively vs 29 (34.9%) post-operatively (p=0.21). One (1.2%) post-operatively had voiding dysfunction diagnosed by an abnormal voiding pattern (p=0.728), which was not statistically significant. Objective voiding dysfunction as determined by adjusted flow rates <10th centile LN and >50 ml PVR was seen in four women (4.8%). Adjusted free flow rates are significantly reduced following insertion of the MONARC TOT, as are some symptoms related to voiding dysfunction. Despite this, satisfaction rates remain high with observed voiding dysfunction or objective measures of voiding dysfunction showing no statistical change in the short term. Long-term follow-up is planned at 1 year.